One type of a conventional adaptive digital aperture compensation and noise cancel circuit carries out aperture compensation and noise cancel as a result of the comparison between a high frequency component of an input video signal and a respective one of a coring threshold value and a limiter threshold value, and between the input video signal and an input threshold value. That is, when the high frequency component of the input video signal is greater in absolute value than the coring threshold value, the aperture compensation is carried out, and, when the high frequency component is less in absolute value than the limiter threshold value, and the input video signal is less than the input threshold value, the noise cancel is carried out. On the other hand, the comparison result does not meet the above conditions, the input video signal is passed through the circuit without any signal processing.
In the high frequency component of the input video signal, generally, there is a level difference having a ratio which is greater than two times between an edge component and a noise component, so that a large level difference is set between the coring threshold value and the limiter threshold value to detect the edge and noise components. That is, the coring threshold value is set to be much greater than the limiter threshold value. Thus, an output video signal which is applied with the aperture compensation or the noise cancel is obtained at an output terminal of the circuit.
However, the conventional adaptive digital aperture compensation and noise cancel circuit has a disadvantage in that a large number of signal bits are required to provide a sufficient gradation of the noise component, because the edge and noise components are transmitted through a common signal line. As a result, a scale of a multiplier for multiplying the high frequency component and a respective one of an aperture compensation gain and a noise cancel gain becomes large.